The present invention relates to the utilization of sound spatialization in audio signals.
The use of B-format measurements, recordings and playback in the provision of more ideal acoustic reproductions which capture part of the spatial characteristics of an audio reproduction are well known.
In the case of conversion of B-format signals to multiple loudspeakers in a speaker array, there is a well recognized problem due to the spreading of individual virtual sound sources over a large number of playback speaker elements. In the worst case, this can lead to significant errors in a listeners localization of these virtual sound sources, especially if the listener is situated off-center in the speaker array. Likewise, in the case of binaural playback of B-format signals, the approximations inherent in the B-format soundfield can lead to less precise localization of sound sources, and a loss of the out-of-head sensation that is an important part of the binaural playback experience.
It is an object of the present invention to provide for an improved form of conversion of 3-D Audio Signals for playback over a set of speakers.
In accordance with a first aspect of the present invention, there is provided an apparatus for converting a spatial soundfield signal component set into a set of loudspeaker driving signals, comprising: a filtering means for splitting each component of the spatial soundfield set into a set of frequency bands; a multiplicity of direction determining means, one for each frequency band, interconnected to the filtering means for determining a current corresponding spatial direction for a corresponding frequency band; a panning means connected to each of the direction determining means for panning a first portion of the spatial sound field to a corresponding set of first speakers feeds as determined by the spatial direction; a residual calculation means interconnected to the filtering means and the direction determining means and adapted to extract substantially the first portion from the spatial sound field signal components so as to provide a residual spatial sound field signal component; a residual decoder means interconnected to the residual calculation means and adapted to transform the residual spatial sound field signal into a corresponding set of second speaker feeds; a mixing means for combining the first and second speaker feeds to produce the set of loudspeaker driving signals.
The spatial soundfield signal component set can comprise a B-format set of signals.
In accordance with a further aspect of the present invention, there is provided a method of rendering a soundfield signal component set into a set of loudspeaker driving signals, comprising the steps of: dividing each of the components into a number of frequency bands; for each frequency band: determining a likely signal direction and magnitude; determining a first speaker output feed set for the likely signal direction and magnitude; subtracting the likely signal direction and magnitude from the soundfield component set so as to form a soundfield residual set; determining a second speaker output feed set for the soundfield residual set; combining the first and second speaker output feed set to form the set of loudspeaker driving signals.
In accordance with a further aspect of the present invention, there is provided an apparatus for converting a spatial soundfield signal set into a set of loudspeaker driving signals, comprising: an input means for taking the spatial input signal; a filtering means for splitting each channel of the spatial input into a set of frequency bands; a multiplicity of direction determining means; a multiplicity of panning means; and a mixing means for combining the outputs of the multiple panning means to create the speaker driving output signals wherein the multiplicity of direction determining means is configured such that one direction determining means is associated with one of the frequency bands, and is attached the the frequency output of all filter banks, and configured to derive the direction of arrival from the short-term intensity and phase of each directional component relative to the intensity and phase of the omni-directional component of the soundfield.
Preferably, the panning means is associated with one of the frequency band and is configured to create output speaker drive signals that substantially reproduce the same soundfield signal with the majority of the sound panned to the nearby speakers.